/Engine/Source/Runtime/Engine/Public/MaterialHLSLTree.h
Create new expressions representing DDX/DDY of this expression
virtual void ComputeAnalyticDerivatives ( [FTree](API\Runtime\Engine\HLSLTree\FTree) & Tree, [FExpressionDerivatives](API\Runtime\Engine\HLSLTree\FExpressionDerivatives) & OutResult ) const